The present invention relates generally to the cooling of heat generating surfaces and objects. More specifically, the present invention relates to apparatuses for dissipating heat generated by such objects. In addition, the present invention relates to cooling of heat generating objects by use of composite materials and devices without the use of external fans to assist in cooling.
In industry, there are various parts and components that generate heat during operation. For example, in the electronics and computer industries, it is well known that computer components generate heat during operation. Various types of electronic device packages and integrated circuit chips, such as the PENTIUM central processing unit chip (CPU) manufactured by Intel Corporation and RAM (random access memory) chips are such devices that generate heat. These integrated circuit devices, particularly the CPU microprocessor chips, generate a great deal of heat during operation which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, a PENTIUM microprocessor, containing millions of transistors, is highly susceptible to overheating which could destroy the microprocessor device itself or other components proximal to the microprocessor.
There are a number of prior art methods to cool heat generating components and objects to avoid device failure and overheating, as discussed above. A block heat sink or heat spreader is commonly placed into communication with the heat generating surface of the object to dissipate the heat therefrom. Such a heat sink typically includes a base member with a number of individual cooling members, such as fins, posts or pins, to assist in the dissipation of heat. The geometry of the cooling members is designed to improve the surface area of the heat sink with the ambient air for optimal heat dissipation. The use of such fins, posts of pins in an optimal geometrical configuration greatly enhances heat dissipation compared to devices with no such additional cooling members, such as a flat heat spreader.
To further enhance air flow and resultant heat dissipation, fans and devices have been used, either internally or externally. However, these external devices consume power and have numerous moving parts. As a result, heat sink assemblies with active devices are subject to failure and are much less reliable than a device which is solely passive in nature.
It has been discovered that more efficient cooling of electronics can be obtained through the use of passive heat pipes which require no external power source and contain no moving parts. Generally, known heat pipes are in the form a vacuum-tight vessel in a particular geometric shape which is evacuated and partially filled with a working fluid. The heat pipe passively transfers heat from a heat source to a heat sink where heat is dissipated. As the heat is conducted into the heat pipe, the fluid is vaporized in an evaporator section creating a pressure gradient in the heat pipe. This forces the vapor to flow along the heat pipe to the condenser section, where the vaporized fluid is condensed and turned back to its fluid state by giving up its latent heat of vaporization. The working fluid is then returned to the evaporator section to repeat the process of removing the heat generated by the heat source. One method used to achieve cooling by use of a heat pipe places the evaporator section at the lower end and the condenser section at the upper end where the heat pipe is in a substantially vertical position. Once the working fluid has been condensed, the liquid flows by gravity back to the evaporator section. Internal wick structures may be used to assist liquid flow back to the evaporator section by capillary action to reduce the effect of gravity on the device.
However, the foregoing known heat pipes suffer from many disadvantages making them inappropriate for many applications. For example, known heat pipes are typically orientation sensitive, particularly those without an internal wicking system. Since heat pipes are charged under pressure with the appropriate media, they cannot be punctured. Therefore, known heat pipes are sensitive to impact. Moreover, it is difficult to insert mold known heat pipes because the pressure of the molding pressure can easily collapse and destroy a heat pipe rendering it useless, particularly if the vacuum is breached.
In view of the foregoing, there is a demand for a heat pipe that is capable of dissipating heat. There is a demand for a heat pipe with no moving parts that can provide heat dissipation without the use of active components. In addition, there is a demand for a heat pipe that can provide greatly enhanced heat dissipation over prior art heat pipes. There is a further demand for a heat pipe that is rugged and more impact resistant than prior art heat pipes.
The present invention preserves the advantages of prior art heat dissipation devices, heat exchangers, heat spreaders and heat pipes. In addition, it provides new advantages not found in currently available devices and overcomes many disadvantages of such currently available devices.
The invention is generally directed to the novel and unique extruded or molded heat pipe. The present invention relates to heat pipes for dissipating heat from a heat generating source, such as a computer semiconductor chip or electronic components on a computer circuit board.
The present invention provides a polymer heat pipe with a carbon core and a method of forming such a heat pipe. The heat pipe includes a substantially pure carbon fiber core and an outer jacket of substantially pure polymer material. The heat pipe is formed by extruding a mixture of a base of polymer material and a plurality of carbon fibers through an extrusion die. The extrusion die is heated into a range of approximately 250-400xc2x0 F. to cause the carbon fiber to migrate to the center of the extrudate and the polymer to migrate outwardly. As a result, a jacket of polymer material is formed around a core of carbon fibers to form a highly thermally conductive heat pipe.
It is therefore an object of the present invention to provide a heat pipe that can provide enhanced heat dissipation for a heat generating component or object.
It is an object of the present invention to provide a heat pipe that can provide heat dissipation for semiconductor devices on a circuit board, such as a motherboard.
It is a further object of the present invention to provide a heat dissipating device that has no moving parts.
Another object of the present invention is to provide a heat dissipating device that is completely passive and does not consume power.
A further object of the present invention is to provide a heat dissipation device that inexpensive to manufacture.
Another object of the present invention is to provide a heat pipe that has a thermal conductivity greater that conventional heat pipe designs.
A object of the present invention is to provide a heat pipe that is easily formable into a wide array of configurations.
Yet another objection of the present invention is to provide a heat pipe that has a thermal conductivity far superior to known heat pipes.